1. Field of the Invention
The present invention relates generally to the placement and retrieval of subsurface equipment in a well. In particular, the present invention relates to means for pumping well equipment through a production tubing string to land the equipment in a side pocket mandrel and to means for subsequently retrieving the landed equipment from the side pocket of the mandrel and returning it to the well surface. The disclosed embodiment of the invention is particularly directed to well completion systems in which the pump-down equipment must be movable through curving sections of tubing.
2. Brief Description of the Prior Art
The typical offshore oil and gas well is equipped and worked from an offshore production platform. Such platforms have been expensive and dangerous to operate resulting in the development of well systems which can be operated from a remote platform or land base. These remotely operated well systems usually require the use of through-the-flowline (TFL) or pump-down equipment and techniques. The well known wire line technique is not suitable for use with many remotely operated wells since the well tubing does not extend directly downwardly from the working area and the force of gravity cannot be employed to lower the wire line equipment.
In many remotely operated marine completions, the tubing extends horizontally along the water bottom beween the operating platform or land base and the wellhead. The direction of movement of equipment pumped through the tubing must therefore change at the wellhead from horizontal to substantially vertical. Since TFL, pump-down equipment includes rigid components which cannot move through a right angle turn, it is conventional in remotely operated completions to form a large radius curve in the tubing at the wellhead thereby reducing the amount of bending or articulation required by equipment moving through the tubing flow line.
Typical side pocket placement tools are relatively long and rigid which prevents them from being moved through curved tubing. If a conventional pump-down placement or retrieval tool is modified by providing joints along its length which permit it to flex as it moves through the curves, the flexibility of the assembly may prevent it from operating properly once it reaches the subsurface location.
Because of the expense of pump-down equipment and because of the substantial financial loss which may result from its inoperability, it is desirable to employ running and pulling tools of simple, reliable design. In this regard, it is advantageous to employ a single basic assembly for both placing and retrieving subsurface equipment so that the number of different components required for operating and maintaining a pump-down system can be reduced.
It is also desirable to be able to retrieve the running assembly with the use of pump-down techniques when the equipment carried by the assembly becomes lodged or is otherwise inoperative.
In a typical well installation, several die pocket mandrels may be included at different locations in the production tubing string. The equipment to be landed in the side pockets of each of the mandrels may be different and for this reason as well as others, some means is necessary for ensuring that the subsurface equipment is landed in the proper mandrel. Moreover, appropriate means are required for preventing the running and retrieving assembly from operating until it is properly positioned relative to the mandrel.